Balanced turbine or pump runner and method of balancing



= Aug. 14, 1934. R. E. B. SHARP BALANCED TURBINE OR PUMP RUNNER ANDMETHOD OF BALANCING Filed Jan. 9, 1932 2 Sheets-Sheet l EEJ.

a a /Z I 9 /4 Y l2 FIE-6 1934. R. E. B. SHARP 1,970,435

BALANCED TURBINE OR PUMP RUNNER AND METHOD OF BALANCING Filed Jan. 9,1932 2 Shets-Shet 2 Patented Aug. 14, 1934 UNITED STATES PATENT OFFICEBALANCED TURBINE OR. PUMP RUNNER .AND METHOD OF BALANCING ApplicationJanuary 9, 1932, Serial No. 585,735

4 Claims.

This invention relates to an improved balanced turbine or pump runnerand to an improved method for balancing the same.

The rotating parts of a hydraulic machine,

5 particularly a turbine, constitute a revolving mass of appreciablemagnitude which must be carefully balanced to avoid destructive orexcessive vibration. The possibility of vibration due to a relativelysmall unbalance of weight is considerably augmented by the fact that therotating parts are generally of very large diameter. For example, it isusual to build turbine runners with diameters ranging up to 18 ft. Someof these runners weigh as high as 100 tons, and

some develop up to 84,000 horsepower per unit, at varying speeds andheads. The speed varies widely for the different units but is commonlybetween 100 and 200 R. P. M. It is thus seen that with factors such asthese to contend with 20 in a great many installations, the problem ofavoiding unbalancing centrifugal forces is one which requires verycareful work. The method disclosed herein, while particularly applicableto large runners, may also be used to advantage in balancing small sizerunnersl In balancing a hydraulic machine runner, it is highly desirableto maintain as nearly as possible the contour of the flow surfaces inaccordance with the predetermined engineering design thereof. Such adesign takes into consideration such matters as the relative velocitybetween the fiow and the runner surfaces and the matter of cavitation ofthe runner blades which can be caused by an improper contour of theblade surfaces. It is also necessary to maintain the designed structuralstrength of the runner and turbine parts.

Heretofore various methods have been employed-for balancing runners ofhydraulic machines particularly hydraulic turbine runners which tendtoward massiveness. One of these methods as applied to the Francis typeof runner is to fill in the crown at various points thereof until therunner is in balance. Another method which is particularly applicable tothe propeller type runner as well also to the Francis runner is toremove metal from the surface of the runner blades. This method has thedisadvantage that it definitely alters the predetermined flow surface ofthe runner blade thus providing abasis for cavitation.

It is an object of my invention to provide an improved method forbalancing runners particularly those of the propeller type withoutadding weight to the runner as is usually done in connection with thecrown of the Francis runner as above described, and without altering thepredetermined design of the flow surface of the runner blades. Inaddition it is a further object to obtain a balanced runner withoutweakening the same from a structural standpoint.

In one specific aspect of the invention I have accomplished the desireddegree of balance without incurring the undesirable features abovementioned, this being obtained herein by removing excess weight from theinterior of the runner blades rather than from the exterior thereof asin the prior practice. Specifically this is best accomplished by gainingaccess to the interior of the blade through the peripheral edge thereof,for instance, as by drilling radially into the interior of the blade.

In the prior art method previously described wherein metal was removedfrom the surface of the blade with the consequent destruction of theperfect blade surface it is impossible for practical reasons to be ableto restore the surface of the blade to its original desired contour asthis would necessitate adding material to the blade at the point wheremetal was removed. However, in my improved method and construction, byremoving a considerable amount of metal from the interior of the bladethrough a relatively small opening in some external part of the blade Iam able to cover this opening with a relatively small amount of suitablematerial without negativing the balancing operation. In the specific useof the invention as applied to a propeller type runner, by removing theinterior metal through the periph-- eral edge of the blade, it is seenthat I not only preserve the original blade surface but also operatethrough a surface (the peripheral edge) which serves no function inguiding the flow over the runner blade other than to maintain clearancewith the runner casing.

A most important feature of the specific aspect of the invention is thatthe material is removed from a point which will give maximum balancingeffect with a minimum removal of material. This is accomplished due tothe material being removed from the interior of the blades adjacent theperiphery thereof, it being understood that the unbalancing forces arecaused by centrifugal forces of unbalanced masses. The centrifugal forcevaries as the square of the speed and hence it is advantageous to removethe material from near the periphery where the speed is the greatest.

It is thus possible in my improved method and balanced runner to obtainall desired advantages with minimum efiort and few, if any, disadvan-110 tages. Other objects and advantages will be more apparent to thoseskilled in the art from the following description of the accompanyingdrawings in which:

Fig. 1 is a vertical section of an adjustable blade propeller typehydraulic turbine, parts of which are shown in elevation;

Fig. 2 is an enlarged fragmentary plan view of a runner showing how myimproved method of balancing is applied;

Fig. 3 is an elevation of the runner hub and one blade, viewed from itsperipheral edge; and

Fig. 4 is an enlarged fragmentary section of a runner blade showing insection two of the interior balancing holes or chambers within theblade.

Fig. 5 is an enlarged fragmentary edge view- Fig. 6 is a section onlines 6.6 of Figs. 2 and 5;

Fig. 7 is a vertical section of a Francis runner balanced in accordancewith my improved method;

Fig. 8 is a' horizontal section taken on line 8-8 'of Fig. '7; and 0Fig. 9 is a fragmentary side elevation of the runner blade and shroudband taken on line 9--9 of Fig.7.

While the hydraulic turbine used for purposes of illustration is of theadjustable blade propellertype, it will of course be understood that theinvention may be applied to other types of turbines whether of theadjustable or fixed blade. The turbine shown may be considered as aconventional type for purposes of this description, and hence it needonly be briefly described as comprising a runner generally indicated at5 mounted on a shaft 6. which is supported in suitable bearings carriedby a head cover 7. This head cover together with a lower distributorring 8, throat ring 9 and a speed ring including the guide vanes 10,guide the flow to the runner from which it is discharged into a suitabledraft tube herein shown as of the spreading type 11. The runner blades12 are suitably adjusted or rigidly supported as. desired by the runnerhub 13. These runner blades may be of any construction usually employed,the general characteristics of which are, that there are relatively fewblades usually six or less, the blades are relatively flat in thedirection of flow thereover, are inclined more nearly to the horizontalthan the vertical and are relatively thin, consistent however with thenecessary strengthto support the column of water flowing through therunner and to impart the necessary torque to the runner shaft.

To balance the runner the direction of unbalance will first bedetermined in accordance with usual procedure whereupon holes 14 will bedrilled into the interior of the blades from the periphery 15. Thenumber of holes, their diameter and the extent of drilling will bedetermined in accordance with the degree of unbalance while thecircumferential distribution of the holes will be determined not only bythe degree of unba l ance but also by the direction or directions ofunbalance and the amount of material that may be safely removed from anyone blade or from adjacent blades. The bending stresses of the bladesare at a, minimum near the periphery of sizes and depths are used onlyto diagrammatie cally illustrate the invention.

.able blade type.

If desired, plugs 16 may be suitably rigidly fastened in the outer endsof the holes to close the same and thus present a smooth continuousperiphery, it being understood that even though irregularities mayappear in the peripheral surface still this will not affect the flowsurfaces of the runner. 1,

Instead of removing metal by drilling, if pre: ferred the metal may beremoved by chipping deep slots 1'7, which are covered by relatively thinrectangular plates 18, fastened in place by welding or other suitablemeans. Such a slot and plate are shown as applied to one of the bladesin Figs. 5 and 6 in which case the slot 1'7 may be relatively long asshown in one of the blades in Fig. 2.

The invention is also applicable to a Francis runner 19, shown in Fig.7, as by drilling holes 20 through the usual shroud ring 21 into blades22 along the neutral axis thereof. The previously outlined advantages ofmy improved methed as applied to the propeller runners are equallyapplicable to the Francis runner. Hence there is no need for furtherdiscussion. I

It will of course be understood by those skilled 100 in the art thatvarious changes may be made in the construction and arrangement of p theinterior blade holes, while the application of the holes may bevariously applied to the different, types of runners whether of thefixed or adjust- The method herein disclosed may also be varied inaccordance with particular conditions without departing from the spiritof the invention as set forth in the appended claims.

' I claim:

1. The method of balancing a runner of a hydraulic machine wherein therunner has a hub supporting a plurality of blades projecting outwardlytherefrom, consisting in first determining the direction of unbalance ofthe runner and then removing material from the interior of a bladethrough the peripheral edge thereof whereby the blade surface over whichthe hydraulic fluid normally flows remains intact.

2. The method of balancing a. runner of a hydraulic machine wherein therunner has a hub supporting a plurality of blades projecting outwardlytherefrom, consisting in first determining the direction of unbalance ofthe runner and then drilling a hole or series of holes of the same ordifferent diameters into the interior of said blade from the peripheraledge thereof whereby the blade surface over which the hydraulic fluid'normally flows remains intact.

3. The method of balancing a. runner of a hydraulic machine wherein therunner has a hub supporting a plurality of blades projecting outwardlytherefrom, consisting in first determining the direction of unbalance ofthe runner, then drilling a hole or series of holes of the same ordifferent diameters into the interior of said blade from the peripheraledge thereof, and

flnally closingv the outer end or ends of the drilled ROBERT E.BRUNSWICK SHARP.-

